Turning to the government's proposed anti-terror laws, he accused Mr Blair of playing politics with the leaders of the opposition parties by appearing to include them in discussions, then attempting to "spin" the outcome.

The government has now revealed its proposals and the Lib Dems would not accept what was on offer, he said.

"There can be no consensus on detaining people for three months without charge. That's a prison sentence by any other name".

He also promised to oppose a new offence of "glorifying terrorism" on the grounds it would not stand up in court.

In a week when the party leadership has been defeated on proposals to cap spending on Europe and part-privatise the Royal Mail, Mr Kennedy received loud applause when he pledged not to transform the Lib Dems into "another Conservative party".

He also spoke up in favour of proportional representation, saying Mr Blair's "final defence" on Iraq was that the war would "help establish democracy".

That argument, Mr Kennedy, said "would have been a damn sight more persuasive if he had started here in Britain first."